Electronic device, in particular mobile telephone, for detecting radiation

ABSTRACT

The invention relates to an electronic device, in particular a mobile telephone ( 1 ), comprising an image sensor ( 4 ) with multiple pixels for capturing an image. The image sensor ( 4 ) is also sensitive to ionizing radiation, in particular pulsed high-energy radiation. The invention additionally relates to a radiation sensor ( 5 ) for measuring the ionizing radiation.

The invention concerns an electronic device, in particular a mobilephone, according to the main claim.

Modern mobile phones often possess an integrated digital camera forcapturing images or films. For this purpose, the integrated digitalcamera has an image sensor (e.g. CCD sensor or CMOS sensor) withnumerous image elements (pixels) arranged in the form of a matrix.Hitherto, such mobile phones with an integrated digital camera have,however, still not been used for measurement of ionizing radiation.

Therefore, the invention is based on the object of using a mobile phonewith an integrated image sensor also for measurement of ionizingradiation.

This object is achieved by means of a corresponding mobile phoneaccording to the main claim.

The invention is based at first on the technical-physical insight thatthe image sensor often integrated in modern mobile phones are not onlysensitive to visible light, but also allows the measurement of ionizingradiation, in particular pulsed high-energy radiation, as occurs, forexample, with computer tomographs (CTs).

The invention therefore comprises the general technical teaching to usethe image sensor in such a mobile phone or in any other electronicdevice with such an image sensor also for measurement of ionizingradiation. The technical realization of this idea is described in thesubsequently published patent application PCT/EP2001005353, so that, toavoid repetition, reference is made to this patent application.

Furthermore, the invention provides an additional radiation sensor inorder to measure the ionizing radiation, wherein it can be, for example,a conventional Geiger-Müller counter tube or a photodiode (e.g. a PINphotodiode) (PIN: Positive Intrinsic Negative). The invention thereforepreferably provides the combination of a conventional image sensor (e.g.CCD sensor, CMOS sensor) with a radiation sensor (e.g. Geiger-Müllercounter tube, PIN photodiode), so that the ionizing radiation ismeasured with two different sensors, which is associated with differentadvantages, which will be described in detail below.

Alternatively, there is also the option that several image sensors arecombined with one another in order to allow a radiation measurement asaccurate as possible, wherein a separate radiation sensor can bedispensed with.

At this point, it is to be mentioned that the electronic device does notnecessarily have to be a mobile phone. The invention rather comprisesalso other types of electronic devices, which have an integrated imagesensor and which are additionally equipped within the context of theinvention with a radiation sensor.

In a preferred exemplary embodiment of the invention, the electronicdevice has an evaluation unit, which is connected on the input side withthe image sensor and with the radiation sensor and calculates from theoutput signals of the image sensor and of the radiation sensor aradiation value (e.g. dosage value, dose rate value), which reflects theionizing radiation.

On the one hand, the evaluation unit detects the pixel values of theindividual image elements (pixels) of the image sensor and calculatestherefrom, in the framework of a statistical evaluation, a correspondingradiation value. The technical details of this evaluation of theindividual pixel values are described in the above-mentioned patentapplication, whose content is therefore to be included in full in thepresent description.

On the other hand, the evaluation unit receives a radiation value fromthe radiation sensor (e.g. Geiger-Müller counter tube, PIN photodiode).

The evaluation unit can then compare, within the context of theinvention, the radiation values measured by the image sensor and theradiation sensor with one another.

The combination of an image sensor with a radiation sensor for radiationmeasurement is advantageous because an image sensor on the one hand anda radiation sensor on the other hand generally have different spectralmeasurement ranges. This means that the image sensor and the radiationsensor are generally sensitive to radiation with different wavelengthsresp. frequencies.

Furthermore, there is within the context of the invention the optionthat the image sensor and the radiation sensor have different powermeasurement ranges. The radiation sensor (e.g. Geiger-Müller countertube) can thus, for example, serve for measurement of lower radiationperformances, whereas the image sensor serves for measurement of highradiation performances.

For example, the image sensor can have a measurement range, whichextends to high radiation performances up to the kilosievert range,whereas the radiation sensor can have a measurement range, which canextend to low radiation performances up to the nanosievert range. Theimage sensor can therefore measure higher radiation, whereas theradiation sensor can measure lower radiation.

The combination of an image sensor with a radiation sensor formeasurement of ionizing radiation is also advantageous because suchsensors generally use different methods of measurement, thus creatingredundancy.

Beyond this, the image sensor and the radiation sensor can be sensitiveto different types of radiation (e.g. alpha radiation, beta radiation,gamma radiation).

In an exemplary embodiment of the invention, the image elements of theimage sensor are at least partially covered with attenuators, whereinthe attenuators attenuate the incident ionizing radiation. Suchattenuators can, for example, be layer-wise and made of copper,aluminium, lead or plexiglass. The thickness of the attenuators variesin this case preferably between the individual image elements (pixels)of the image sensor, which allows for a corresponding statisticalevaluation a highly accurate determination of the spectral energydistribution of the incident ionizing radiation. For example, theattenuators can have a thickness, which expands wedge-shaped from a sideof the image sensor to the opposite side of the image sensor, so thatthe incident ionizing radiation is attenuated on the one side of thewedge-shaped attenuator only slightly, whereas the incident ionizingradiation on the opposite side of the wedge-shaped attenuator isattenuated essentially stronger.

Such attenuator can be used within the context of the invention also forthe radiation sensor.

Moreover, a radiation filter can be arranged in the radiation path ofthe radiation sensor and/or of the image sensor.

It should also be mentioned that the measuring sensitivity of the imagesensor is generally temperature-dependent. In a preferred exemplaryembodiment of the invention, a temperature sensor is therefore providedfor in order to detect the temperature of the image sensor and/or of theradiation sensor. The evaluation unit then takes into account thetemperature of the image sensor measured by the temperature sensor inorder to compensate for the temperature fluctuations during themeasurement.

Moreover, the electronic device according to the invention canadditionally have an active cooling element (e.g. a Peltier element) inorder to actively cool the image sensor and thereby to increase themeasuring sensitivity of the image sensor. Triggering of the activecooling element can in this case take place depending on the measuredtemperature of the image sensor in the framework of a control operationor a feedback control.

Furthermore, a converter (e.g. a scintillator) can be arranged in theradiation path of the image sensor and/or of the radiation sensor, whichconverter converts the incident radiation from a badly detectablewavelength range into a better detectable wavelength range. Theapplication of such a converter therefore allows the measurement ofincident radiation in a wavelength range, in which the image sensorresp. the radiation sensor is insensitive.

During read-out of the image sensor, the problem can occur that theimage sensor has a short dead time, so that no radiation measurement ispossible within the dead time. During the measurement of pulsedradiation, there is, however, the option that the individual radiationpulse each fall in the dead time of the image sensor, so that theincident radiation is not detected.

To avoid such read-related dead times, it is provided for in a variantof the invention that several image sensors are combined with oneanother. This has the advantage that the dead time of the individualimage sensor generally has no temporal overlap, so that at least one ofthe image sensors is sensitive at any time and allows radiationmeasurement.

Another solution to this problem of the dead times of image sensorsconsists in the application of the so-called ERS technology (ERS:Electronic Rolling Shutter). In this process, the individual imageelements (pixels) of the image sensor are each scanned and saved line byline, so that the image sensors are each insensitive only in a singleline, whereas the other lines of the image sensor are sensitive and thenallow a radiation measurement. In this manner, in particular for themeasurement of pulsed radiation, it is prevented that the image sensoris fully insensitive to a radiation pulse.

During the radiation measurement, it must be taken into account that themeasurement result depends on the alignment of the respective radiationsensor and on the positioning of the radiation sensor. So, for example,the user of a mobile phone with an integrated radiation sensor canshadow off the radiation sensor with his body, whereby the radiationsensor measures a falsified radiation value. In a variant of theinvention, the device that serves for radiation measurement thereforehas several radiation sensors, which are spatially arranged in adistributed manner and/or are oriented in different directions. Theevaluation unit can then evaluate the output signals of the differentradiation sensor in order to suppress disturbance variables.

Beyond this, there is the option that the radiation sensor can beoriented in the device in different directions relative to the device,wherein the spatial orientation of the radiation sensor in operation canbe changed. For example, a servomotor can be provided for this purpose,which orientates the radiation sensor in the desired direction.

Furthermore, there is also within the context of the invention theoption that several image sensors are combined with one another in orderto allow a radiation measurement as accurate as possible, wherein aseparate radiation sensor can also be dispensed with. This is essentialfor a spectral measurement. For example, the second image sensor can becovered partially or fully by a scintillator. Furthermore, there is theoption to combine a radiation sensor with several image sensors.

The device for radiation measurement according to the invention issuitable in particular for the measurement of the radiation exposure forairplane crews, which are exposed to a significant cosmic radiation, inparticular during long-haul flights. The invention therefore alsocomprises a flying object, such as an aircraft or a space vehicle, withan electronic device for radiation measurement according to theinvention.

Other advantageous developments of the invention are characterized inthe sub-claims or are explained in more detail below together with thedescription of the preferred exemplary embodiment of the invention onthe basis of the figures. The figures show as follows:

FIG. 1 a front view of a mobile phone with an integrated digital cameraaccording to the invention and a likewise integrated radiation sensor,

FIG. 2 a schematic block diagram of the components of the mobile phonefrom FIG. 1 serving for radiation measurement,

FIG. 3 a schematic cross-section representation of the image sensor ofthe mobile phone from FIG. 1,

FIGS. 4 a, 4 b the radiation measurement method of the mobile phone inthe form of a flow chart.

FIG. 1 shows a front view of a mobile phone 1, which is structured to agreat extent conventionally and has inter alia a LCD display 2, aloudspeaker 3, an image sensor 4 in the form of a digital camera as wellas, additionally, a radiation sensor 5 in the form of a PIN photodiode.Apart from the radiation sensor 5, the mobile phone 1 corresponds to theprior art, so that a detailed description of the structure and mode ofoperation of the conventional constituent elements of the mobile phone 1can be dispensed with.

The image sensor 4 serves, in addition to the conventional capturing ofimages or films, for the measurement of a radiation value of an ionizingradiation in conjunction with the radiation sensor 5, as will beexplained below with reference to the schematic block diagram in FIG. 2.

So, the image sensor 4 has a plurality of image elements (pixels), whichare arranged in the form of a matrix in lines and columns and deliver adigital image. The individual pixel values of the individual imageelements of the image sensor 4 are fed to a statistics unit 6, whichcalculates a radiation value D₁ within the context of a statisticalevaluation of the image values of the individual image elements (pixels)of the image sensor 4, wherein, for example, the radiation value can bethe dose energy or the dose rate of the incident radioactive radiation.

The radiation sensor 5 (e.g. PIN photodiode) likewise calculates acorresponding radiation value D₂, wherein both radiation values D₁ andD₂ are supplied to a computing unit 7, which determines a uniformradiation value D and then transmits it via a phone module 8 (e.g. GSMmodule: Global System for Mobile Communications) and an antenna 9 to acentral monitoring device, which then evaluates the radiation values Dprovided by a plurality of such mobile phones 1.

Moreover, the mobile phone 1 still has a GPS module 10 (GPS: GlobalPosition System), which determines the geographical position of themobile phone 1 with the help of the satellite-based GPS navigationsystem. The geographical position of the mobile phone 1 determined inthis manner is then likewise transmitted together with the radiationvalue D via the phone module 8 and the antenna 9 to the centralmonitoring device. The central monitoring device can then create aradiation map by means of the value pairs transmitted by the numerousmobile phones 1 from the radiation value D and the associatedgeographical position of the respective mobile phone 1, which radiationmap reflects the geographical distribution of the radiation value.

For the radiation measurement, the mobile phone 1 takes into account thetemperature dependency of the measurement through the image sensor 4.The mobile phone 1 therefore has a temperature sensor 11, which measuresthe temperature of the image sensor 4 and transmits a correspondingtemperature value T_(CCD) to the computing unit 7. The computing unit 7then compensates for any fluctuations of the temperature value T_(CCD)when determining the radiation value D in order to allow a determinationof the radiation value D as temperature-independent as possible.

Moreover, the temperature value T_(CCD) measured by the temperaturesensor 11 is supplied to an actuator 12, which controls a coolingelement 13 (e.g. a Peltier element) in such a way that the coolingelement 13 acts with a certain refrigerating power P_(COOL) onto theimage sensor 4 in order to maintain the temperature value T_(CCD) of theimage sensor 4 as constant as possible and thereby to avoidtemperature-related measurement inaccuracies to the greatest possibleextent.

FIG. 3 shows a schematic cross-section through a modification of theimage sensor 4 in a housing of the mobile phone 1. For thismodification, a wedge-shaped attenuator 14 is arranged in the radiationpath before the image sensor 4, the thickness of which enlargeswedge-shaped from a side of the image sensor 4 to the opposite side ofthe image sensor 4. The attenuator 14 is, for example, made of copper,aluminium, lead or plexiglass and attenuates the incident radioactiveradiation depending on the respective thickness of the attenuator 14more or less, which allows a spectral evaluation of the incidentradioactive radiation. So, the image elements (pixels) of the imagesensor 4 on the right side in the drawing primarily measure radioactiveradiation with a relative high energy, which is sufficient to penetratethe layer of the attenuator 14 on this relatively thick side. On theleft side in the drawing, the image elements of the image sensor 4measure, in contrast, also low-energy radiation, since the attenuator 14is very thin there.

The FIGS. 4 a and 4 b show the operating method according to theinvention for the mobile phones 1.1-1.4 in the form of a flow chart,wherein only the process steps are represented and described, with whichthe evaluation unit 7 determines the radiation value D₁ in conjunctionwith the statistics unit 6 from the pixel values of the image sensor 4.

At first, the drawings show an image sensor 15 with numerous imageelements arranged in the form of a matrix for radiation measurement. Theimage sensor 15 can, for example, be a CCD sensor or a CMOS sensor.

A step 16 comprises a value entry of the images measured by the imagesensor 15 with a frame rate of 40-60 fps (frames per second).Alternatively, a frame rate of 15-24 fps is, for example, also possible.Optionally, single images are also possible, then if necessary withshutter times, which correspond to partial image capturing, orconversely time exposures with pretty large shutter times.

The measured images are then saved in a step 17 in an image memory.

Subsequently, in a step 18, a differentiation takes place between theactual image saved in step 17 and a reference image saved a in a step19, wherein a reference memory contains an average brightness per imageelement (pixel) from the previous captured images. The thus reachedaveraging can take place depending on the actual difference, for exampleaccording to the following formula:

Ref=Ref·n+new pixel·m(n+m)

-   with-   Ref: brightness of the reference image-   n: weighting factor for taking into account the reference image with    n+m=1-   m: weighting factor for taking into account the new image with n+m=1-   new pixel: brightness of the new image

The difference thus determined is then compared in a step 20 with anupper limit value and a lower limit value, wherein a counting event istriggered when the measured difference value lies between the upperlimit value and the lower limit value.

Optionally, there is the option of a memory 21 for pixel noiserepresented in FIG. 4 b, which is filled in a calibration process 22with the noise values per pixel. To do so, several measurements arecarried out in the dark and without any additional radiation. Theindividual differences between the current image and the last image areadded up with a matrix (noise values per pixel) and then e.g. maximumvalues resp., after statistical evaluation, the determined values aresaved (Gaussian distribution taking into account the incident backgroundradiation). Furthermore, an external threshold 23 can be added, which isadded up to the pixel threshold from the memory 21 in a step 24, whichprovides for more stable results.

A threshold value comparison 25 then provides an analogue or digitalsignal when threshold values are exceeded resp.—in case of negativesign—fallen short of. In a step 26, the counting events are then addedup over a certain unit of time.

Thereupon, in a step 27, the number of counting events (counts) iscalculated per minute.

Via a calibration table 28, the assignment to a dose rate (e.g. based onthe counts per minute) resp. dose (from the total number of counts) isthen created. The calibration table can be created for a group ofsensors or created individually through a measurement process withcalibrated radiation source. Optionally, a correction factor can beprovided for simplified calibration with one or two points.

As a result, in a step 29, a dose rate and, in a step 30, a dose is thenoutput.

Furthermore, there is also the option for an image processing 31 fordetermining the energy value of the incident photons. Thus, low-energyphotons generally trigger only a counting event in a single imageelement of the image sensor 4. High-energy photons lead in contrast to acrosstalk between neighboring image elements of the image sensor 4, sothat a group (cluster) of several neighboring image elements of theimage sensor 4 trigger a counting event. Through the image processing31, such groups of activated image elements can then be determined,whereby a spectral distribution can be calculated in an approximatemanner. The values thus obtained are compared with a data base 32 of theenergy values, whereupon a spectrum of the incident radiation is thenoutput in a step 33.

The invention is not limited to the previously described preferredexemplary embodiment. Instead, many variants and modifications arepossible, which also make use of the concept of the invention and thusfall within the scope of protection. Furthermore, the invention alsoclaims protection for the subject matter and the individual features ofthe subclaims independently of the features of the claims to which theyeach refer.

LIST OF REFERENCE SIGNS

-   1 Mobile phone-   2 LCD display-   3 Loudspeaker-   4 Image sensor-   5 Radiation sensor-   6 Statistics unit-   7 Computing unit-   8 Phone module-   9 Antenna-   10 GPS module-   11 Temperature sensor-   12 Actuator-   13 Cooling element-   14 Attenuator-   15 Image sensor-   16 Step “Value entry”-   17 Step “Save”-   18 Step “Differencing”-   19 Step “Reference image”-   20 Step “Threshold value testing”-   21 Memory for pixel noise-   22 Calibration process-   23 External threshold-   24 Step “Summation”-   25 Threshold value comparison-   26 Step “Summing-up per unit of time”-   27 Step “Counts per minute”-   28 Calibration table-   29 Output Dose rate-   30 Output Dosage-   31 Image processing-   32 Database of the energy values-   33 Output Spectrum-   T_(CCD) Temperature value of the image sensor-   D1 Radiation value-   D2 Radiation value-   D Radiation value

1-20. (canceled)
 21. An electronic device comprising: a) an image sensorwith several image elements for capturing an image, wherein the imagesensor is also sensitive to ionizing radiation, and b) at least one ofan additional radiation sensor and an additional image sensor adaptedfor measurement of the ionizing radiation.
 22. The electronic deviceaccording to claim 21, wherein the device further comprises anevaluation unit, which is connected on an input side with the imagesensor and with the additional radiation sensor and calculates aradiation value from output signals of the image sensor and outputsignals of the additional radiation sensor, which value reflects theionizing radiation.
 23. The electronic device according to claim 22,wherein the evaluation unit statistically evaluates the output signalsof the image elements of the image sensor.
 24. The electronic deviceaccording to claim 22, wherein the evaluation unit compares the outputsignals of the image sensor with the output signals of the additionalradiation sensor.
 25. The electronic device according to claim 21,wherein the image sensor is a CCD sensor or a CMOS sensor.
 26. Theelectronic device according to claim 21, wherein the additionalradiation sensor is a Geiger-Müller counter tube or a photodiode. 27.The electronic device according to claim 21, wherein the image sensorand the additional radiation sensor have different spectral measurementranges.
 28. The electronic device according to claim 21, wherein theimage sensor and the additional radiation sensor have different powermeasurement ranges.
 29. The electronic device according to claim 27,wherein the image sensor has during the measurement of the ionizingradiation a measurement range, which extends into a kilosievert range.30. The electronic device according to claim 27, wherein the additionalradiation sensor has during the measurement of the ionizing radiation ameasurement range, which extends into a nanosievert range.
 31. Theelectronic device according to claim 21, wherein the image sensor andthe additional radiation sensor apply different measurement methods tocreate redundancy.
 32. The electronic device according to claim 21,wherein the image sensor and the additional radiation sensor aresensitive to different types of radiation of the ionizing radiation. 33.The electronic device according to claim 21, wherein the image elementsof the image sensor and/or of the additional radiation sensor arecovered at least partially by an attenuator, which is adapted toattenuate incident ionizing radiation.
 34. The electronic deviceaccording to claim 33, wherein the attenuator is adapted to attenuatethe incident radiation to a different degree.
 35. The electronic deviceaccording to claim 34, wherein the attenuator has a thickness, whichextends wedge-shaped from a side of the image sensor adjacent theadditional radiation sensor to an opposite side of the image sensoropposite the additional radiation sensor.
 36. The electronic deviceaccording to claim 33, wherein the attenuator comprises at least one ofthe following materials: a) copper, b) aluminium, c) lead, and/or d)polymethyl methacrylate.
 37. The electronic device according to claim33, wherein a) attenuators of the individual image elements of the imagesensor have different spectral attenuation characteristics, and b) theevaluation unit calculates from output signals of the individual imageelements of the image sensor a spectral energy distribution of incidentionizing radiation.
 38. The electronic device according to claim 21,wherein a radiation filter is arranged in a radiation path of theadditional radiation sensor.
 39. The electronic device according toclaim 21, wherein a) the device has a temperature sensor adapted formeasurement of a temperature of the additional radiation sensor and/orof the image sensor, and b) the evaluation unit is connected on an inputside with the temperature sensor and takes the measured temperature intoaccount for calculation of a radiation value in order to compensate fortemperature fluctuations.
 40. The electronic device according to claim21, further comprising an active cooling element adapted for activecooling of the image sensor in order to increase a measuring sensitivityof the image sensor.
 41. The electronic device according to claim 21,wherein a converter is arranged in a radiation path of the image sensorand/or of the additional radiation sensor, which converter is adapted toconvert incident radiation from a badly detectable wavelength range intoa better detectable wavelength range in order to extend a measurementrange.
 42. The electronic device according to claim 21, wherein acombination of several image sensors is provided for to avoid dead timedue to reading-out.
 43. The electronic device according to claim 21,wherein the image sensor has numerous image lines each of whichcomprises several image elements, wherein the image sensor is adapted toscan and save the image line by line, so that the image sensor isinsensitive each time only in a single line.
 44. The electronic deviceaccording to claim 21, wherein several additional radiation sensors arespatially arranged in a distributed manner and/or are oriented indifferent directions.
 45. The electronic device according to claim 21,wherein the image sensor can be aligned in different directions relativeto the device.
 46. The electronic device according to claim 45, whereina servomotor is provided for motorized alignment of the image sensor.47. The electronic device according to claim 21, wherein, in addition tothe image sensor, several different additional radiation sensors areprovided for.
 48. The electronic device according to claim 47, whereinthe different additional radiation sensors are Geiger-Müller countertubes.
 49. The electronic device according to claim 47, wherein thedifferent additional radiation sensors are photodiodes.
 50. A flyingobject with an electronic device according to claim 21 for measurementof radiation exposure of a crew of the flying object through cosmicradiation.
 51. The flying object according to claim 50, wherein theflying object is an aircraft.
 52. The flying object according to claim50, wherein the flying object is a spacecraft.
 53. The electronic deviceaccording to claim 21, wherein the image sensor is sensitive to ionizingradiation which is pulsed radiation up to a kilosievert range.